1. Field of the Invention
This invention relates to an impact energy absorption system, and in particular to a crushable tubular assembly for efficient and controllable energy absorption.
2. Background of the Invention
In current vehicle structures, and particularly in front-end structures, it has become increasingly difficult to obtain package space for components that absorb impact energy created during a vehicle crash. Conventional designs for absorbing high-energy impacts, such as that described in U.S. Pat. No. 3,831,997 to Myers, typically include tubular structures that are made from high strength materials like various high strength steels. These tubular structures may be designed as vehicle rails, or may be separately positioned in a fore/aft direction of the vehicle to absorb the energy of a fore/aft collision. However, such designs have a tendency to buckle laterally if the load is offset, that is, if the load is not concentric with the tube. Moreover, because of the limited package spaces available, with limited frame selection allowed, improving the axial strength of such structures tends to increase the degree of lateral instability of the tubes.
Other conventional designs include tubular assemblies that have structures for initiating deformations in the assembly, such as described in U.S. Pat. No. 5,914,163 to Browne. These features include slits or other structures to initiate longitudinal splitting, tearing, or peeling of the tubular assembly. While providing such structures may assist in controlling the energy absorbed in an impact, the overall axial strength of such tubular structures may be compromised.
Still other systems for absorbing frontal impact energy include entire redesigns of an automotive vehicle body structure, such as, for example, the vehicle body structure described in U.S. Pat. No. 6,312,038 to Kawamura, et al. Such designs may include extensions of the vehicle body/frame in the fore/aft direction in order to accommodate one or more energy absorbing members. Such redesigns, however, are expensive to develop and are not compatible with automobiles in present production. In particular, presently produced automobiles may not have the necessary package space available for housing an increased number of absorbing members, or tubes.
There is thus a need for an impact energy absorption system that will minimize or eliminate one or more of the above-mentioned deficiencies.
The present invention provides an improved impact energy absorption system, and a method for absorbing impact energy.
An impact energy absorption system in accordance with the present invention comprises an assembly of crush tubes. The crush tube assembly includes a first tube disposed about a second tube. A third tube having convolutions is also disposed within the first tube, and may be interposed between the first and second tubes. The third tube may alternatively be disposed within the second tube. The convolutions of the third tube support the axial integrity, and minimize lateral bucking of the first and second tubes during the absorption of impact energy. Additional alternating layers of smooth and convoluted tubes may be alternatively disposed within the assembly to provide further strength and control for absorbing energy.
A method for absorbing impact energy is also provided. The method includes the steps of providing a first tube substantially free from convolutions, disposing within said first tube a second tube substantially free from convolutions, interposing between said first and second tubes a third tube having convolutions; and impacting said first, second, and third tubes.
An impact energy absorption system in accordance with the present invention has several advantages as compared to conventional systems. The inventive device provides the axial strength of a conventional smooth, or unconvoluted tube and the energy absorption control of a convoluted tube. The inventive device, therefore, can absorb high-energy impacts that may be offset, while reducing the tendency to buckle laterally. Additionally, the inventive device maximizes the use of available package space by disposing each crush tube about one another. Accordingly, the present invention is able to absorb broad ranges of crush energy and maintain its lateral stability during a crash.